Meiosis allows a living organism like us, humans, to produce sperm and eggs, which allows for fertilisation. Spoiler alert this is how baby’s are made. A big idea in biology 💡 is this idea of the continuation of the species. Essentially, every process should be in service to continuing the species. In our experience, our students have understood this concept best through doing meiosis exam questions.
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Meiosis is like a dance party where your cells are the dancers! When it’s time to party, your cells get ready by making an extra copy of all their DNA. This way, each cell has twice as much DNA as normal.
Next, the cells start to divide, just like they would during regular cell division. However, instead of just dividing once, they divide twice! This creates four new cells, each with half the normal amount of DNA.
This might seem confusing, but it’s actually really important. By dividing and halving the amount of DNA, your cells can mix and match different combinations of genes. This creates lots of diversity, which is helpful when it comes to reproduction and survival.
So, to sum it up, meiosis is a special kind of cell division that helps create diversity and keep things interesting in the world of cells!
Meiosis can be broken into a series of steps. Simply put it is the process through which one cell is divided into four cells. You do this by splitting a cell once, then splitting those two cells again. The first time you split the cell you halve the amount of genetic information, the second time you split it the genetic information is preserved. Lets say for a normal human cell it contains 46 chromosomes. A human sperm 💦 or egg 🍳 cell contains half of that, so it contains 23 chromosomes. A normal cell is called a diploid cell and a sperm or egg cell is called a haploid cell.
Interphase is not apart of meiosis or mitosis and it occurs to prepare the cell for division. The cell prepares through growing, replicating it’s DNA and preparing to divide 🦠.
There are four phases of meiosis. These are prophase, metaphase, anaphase and telophase. These occur a total of two times. A good way to remember these four phases and the order they occur is the cat 🐈Pee’d on the MAT.
Prophase is the first step in meiosis, DNA has been replicated so it pairs up at the centromere. Additionally, the chromatin in the cell is condensed and the nucleolus disappears 👻.
Metaphase is when the chromosomes are lined up at the equator of the cell, the genetic information is at its second most condensed stage.
Anaphase involves the pulling apart of the chromosomes into sister chromatids by the spindle fibres which are protrusion from the centriole which are found at both ends of the cell. The daughter chromatids are therefore transported to opposite poles of the cell.
Telophase is the final stage in mitosis and it involves the uncoiling of chromosomes to form chromatin. Hence preparing the genetic material to direct metabolic activities for the new cells. Additionally, the spindle breaks down, and new nuclear envelopes envelop the DNA 🧬.
Additionally, cytokinesis occurs which involves the cell membrane being pinched inwards for the cell hence forming to new cells.
Meiosis differs in that the aboves processes Prophase, metaphase, anaphase, telephase and cytokenesis occurs twice. Therefore, 4 haploid cells form from 1 diploid cell. These haploid cells contain half the amount of DNA as the parent cell. These form gametes (sperm cells and egg cells), which can later combine and form a diploid cell which will replicate through mitosis to form a new organism 👶.
Meiosis exam Questions 💯
Question 1.
A student states:
‘All cells in the body are genetically identical’
Evaluate the validity of the statement, explain your reasoning [3 marks]
Question 2.
Compare and contrast mitosis and meiosis
Question 3.
Question 28b) from 2019 HSC Exam
Question 4.
Answers.
Question 1.
The majority of an organisms cells are genetically identical, however, gametes are not genetically identical as well as cancer cells.
Meiosis – 1 diploid parent cell forms four genetically different haploid granddaughter cells. This genetic diversity can come about from crossing over between metaphase and anaphase.
Mitosis – 1 diploid parent cell forms two genetically identical daughter cells.
Question 2.
| Reason | Marks |
| Provides 2 differences:Prophase, metaphase, telophase and anaphase occur twice in meiosis and once in mitosisMitosis has 2 genetically identical daughter cells and meiosis has four genetically different granddaughter cells | 2 |
| Provides 2 similarities: Both result in formation of daughter cellsBoth involve DNA doubling up at some point | 2 |
Question 4.
HSC question 2020 Q19
A
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